The invention relates to an insert coupling that includes a sleeve-shaped coupling body having a housing, a tubular insert part having a circumferential retaining rib, and a coupling element having a ring shaped body and which can be axially inserted in the housing to be axially fixed in an insert position. The tubular insert part is inserted through the coupling element into the sleeve-shaped coupling body. The coupling element includes at least one engagement hook intended for the positive engagement with the retaining rib of the insert part.
Insert couplings of this type are utilized for example in vehicle construction with fuel lines and serve to establish a connection between a tubular insert part provided with a circumferential retaining rib and a sleeve-type coupling body. The insert part can be manufactured of plastic or metal and be the end of a line or the connection spigot on a housing. The coupling element is usually manufactured of plastic and mounted on a line but can also be a part of a housing.
Insert couplings of this type are characterized by a locking mechanism that is effective between the coupling body and the insert part and are intended to form a sealing connection between the respective line elements to be coupled. They have become known in numerous forms wherein particular attention has been attached to functional reliability and characteristics of assembly-related handling.
From patent document DE 4300037 C1 an insert coupling of the type mentioned above is known wherein the locking mechanism between the coupling body and the insert part is constructed of a component which is displaceable radially to the main axis and intended for engaging behind the retaining rib of the insert part. Comparable insert couplings are known from DE 197 22 842 C2, DE 10 2004 062 887 B3, EP 17 19 944 A2, US 2004/0189001 A1 and DE 10 2006 019 257 A1. With these insert couplings it is disadvantageous that correct engagement of the insert part in the coupling body is not definitely evident from the outside in all cases. The assembly of the insert couplings must take place in two directions so that the expenditure for automatic assembly is clearly increased. The number of necessary components is also high.
A further insert coupling is known for example from DE 44 13 346 C1, whose locking mechanism is realized through a sleeve which is axially inserted in the coupling body and axially displaceable to a limited extent in the slide-in position. The sleeve consists of a ring positioned in the sleeve base of the coupling body from which four webs extend parallel to the axis in even circumferential distribution and in the direction of the open end of the coupling body, of which two carry engagement hooks located diametrically opposite each other intended on the inside to interact with the retaining rib of the insert part. All webs are provided on the radial outside with shoulders which are accommodated axially moveable to a limited extent in recesses of the coupling body so that via two projections molded on the outside to the webs not provided with engagement hooks and protruding from the coupling body the sleeve can be gripped and moved axially relative to the coupling body in order to release the coupled state of the insert part with the coupling body.
A disadvantage with this insert coupling is that correct engagement is not visible from the outside. Furthermore, the sleeve forms an active surface for the seal embodied by means of O-rings. Due to the required axial displaceability of the sleeve, the inserted O-rings, upon introducing the insert part, are pushed into an axial end position and, upon the intended exposure of the coupling to internal pressure, into an opposite axial end position. In the front region, which the O-rings on their path have to cover, dirt is able to enter from the outside. The O-rings perform this displacement with every releasing and establishment of a coupled state so that there is a risk that the O-rings twist and/or dirt particles become embedded in the sealing regions during this movement as a result of which secure tightness is no longer guaranteed. This is all the more significant since this type of coupling among other things is also utilized in fuel lines. A leak test during series production upon the assembly of the coupling as a unit is not possible since the O-rings assume their active position only in the assembled state.
The insert coupling known from DE 39 29 723 is characterized by a sleeve part and an insert part provided with a circumferential retaining rib, wherein the sleeve part is material-connected with a ring-shaped shoulder part carrying an arrangement of reed-like restraining elements orientated from inwardly in the direction of the base of the sleeve part, and wherein in the coupled state these restraining elements are intended for the positive connection engagement behind the retaining rib. The shoulder part on its side axially facing away from the restraining elements forms an active surface for supporting a sealing arrangement, which is otherwise axially supported on the sleeve part. For releasing the coupled state a sliding sleeve is provided whose face end is intended and equipped for the radial engagement below the restraining elements and thus for the releasing of the engagement with the retaining rib of said restraining elements. This insert coupling is thus characterized by a multiplicity of components and thus by a comparatively complicated construction.
Finally a further insert coupling is known from DE 37 27 858 which consists of a sleeve-like coupling body on its one end intended for joining with a hose and an insert part intended for insertion in said hose intended for joining with a line at its end facing away. The end of the coupling body facing the insert part is characterized by a ring element on whose inside block-like locking segments are molded which are intended for the positive engagement behind a holding rib circumferentially arranged on the insert part. The ring element is in connection with the coupling body by way of two webs which extend parallel with the axis and are located diametrically opposite each other, said ring element is further characterized by a cylindrical mounting space on the inside which interacts with two sealing rings each accommodated in slots of the insert part. Releasing of the coupled state is thus possible through the oval deformation of the ring element. This insert part requires utilization of a special insert part which simultaneously acts as carrier of the sealing rings. A special assembly sequence is thus required. Although there are recesses between the mentioned webs—whether there is a correct state of engagement between the retaining rib and the locking segments is at least through mere inspection not easily detectable with adequate reliability.